Senior-clinician companion to introductory Pharmacology notes. Educational use only; verify every prescription in current authorised resources and local policy.
A Word From Your Senior
Prescribing is a clinical experiment performed on one person. State the indication, predict benefit and harm, account for vulnerability, and define how you will know whether to continue, adjust, or stop.
Pharmacokinetics and Pharmacodynamics
Absorption, distribution, metabolism, and excretion shape concentration over time. Bioavailability, protein binding, volume of distribution, hepatic function, renal function, age, pregnancy, critical illness, interactions, and formulation can alter exposure.
Pharmacodynamics links concentration to effect. Agonism and antagonism are useful starting ideas, but receptor occupancy, intrinsic activity, signalling bias, tolerance, therapeutic window, and off-target effects matter. Dose-response is not always linear.
A Safer Prescribing Sequence
- Define indication and treatment goal.
- Check allergy details, pregnancy possibility, comorbidity, organ function, current medicines, substances, and prior response.
- Select drug, route, formulation, and duration from current guidance.
- Check interactions, duplication, contraindications, monitoring, and deprescribing plan.
- Explain expected benefit, common harms, serious warning symptoms, and adherence barriers.
- Reconcile medicines at every transition of care.
Bedside Case
An older adult becomes confused and falls after several medicines were added. Resist searching for one "bad drug." Review cumulative anticholinergic and sedative burden, blood pressure, renal function, recent dose changes, over-the-counter products, alcohol, withdrawal risk, and the original indication for each medicine. Deprescribing is treatment, but abrupt cessation can also harm.
Antimicrobial Stewardship
Antibiotics treat susceptible bacteria, not viral syndromes. Before prescribing, consider syndrome, severity, source control, likely organisms, local resistance, cultures, allergy validity, renal/hepatic function, and the narrowest effective regimen. Review at a defined time to stop, narrow, switch route, or revise diagnosis.
Accuracy Guardrails
- "The dose makes the poison" is useful but incomplete: timing, route, host, interactions, and cumulative exposure matter.
- Therapeutic drug monitoring is drug- and context-specific; a number without sampling time can mislead.
- Avoid unsafe abbreviations and trailing zeros; follow local prescription standards.
- Never copy a dose from an educational note.
- Adverse drug reactions should be documented precisely and reported through the applicable pharmacovigilance system.
Trusted Starting References
- WHO Medication Without Harm (opens in a new tab)
- WHO AWaRe antibiotic book (opens in a new tab)
- Current national formulary, local antimicrobial guideline, and product information.